1. Field of the Invention
This invention relates to the field of data processing. More particularly, this invention relates to data processing systems including registers for storing data words to be manipulated by an arithmetic logic unit and for storing result data words produced by the arithmetic logic unit.
2. Description of the Prior Art
It is known to provide data processing systems having a plurality of registers and an arithmetic logic unit for reading and writing to those registers. It is a constant aim within data processing systems to increase the speed with which they operate. One technique for increasing speed is to adopt an instruction set with relatively few instructions, but with the hardware configured to run each of those instructions at high speed. This design philosophy is often referred to as reduced instruction set computing (RISC). Within a RISC system it is desirable that those few instructions that are provided have a great degree of flexibility and utility.
One instruction that is sometimes useful is to perform a calculation but not to store the result to a working register. One way to achieve this is the provision of a dedicated sink register to which the unwanted result may be written and whose contents are fixed and/or always zero. However, this sync register uses up a location in the register address space that is unavailable for normal processing. Furthermore, writing to the sink register may consume unnecessary power.